SQLITE - Delete rows with self join? - sqlite

I am trying to delete all rows in a simple table that have a duplicate value except for the duplicate with the highest id.
Table:
CREATE TABLE IF NOT EXISTS [Expression] (
[ID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[Value] VARCHAR(2048) NOT NULL
)
Attempted Queries:
DELETE Expression
WHERE EXISTS (
SELECT 1
FROM Expression Exp2
WHERE Expression.Value=Exp2.Value
AND Expression.Id < Exp2.Id)
fails with
"SQL logic error or missing database near "Expression":syntax error"
DELETE Exp1
FROM Expression Exp1
INNER JOIN Expression Exp2
ON Exp1.Value=Exp2.Value AND Exp1.Id < Exp2.Id
fails with
"SQL logic error or missing database near "Exp1":syntax error"
What syntax do I need to use?

Don't forget the FROM.
DELETE command
DELETE FROM Expression
WHERE EXISTS (
SELECT 1
FROM Expression Exp2
WHERE Expression.Value=Exp2.Value
AND Expression.Id < Exp2.Id
);

You can do this with many ways:
1) USING CTE:
WITH CTE AS (
SELECT ID, VALUE, ROW_NUMBER() OVER(ORDER BY Value) as RowNum
FROM Expression
)
DELETE
FROM CTE
WHERE ROWNum >1
2) USING Temp tables: Same concept

DELETE t1 FROM contacts t1 INNER JOIN contacts t2 WHERE t1.id < t2.id AND t1.email = t2.email;

Related

I need only one unique result in Oracle sdo_nn Update sentence ,

I need Only one unique result from tableB.Field to tableA.Field
I am using sdo operator sdo_nn, this is the code:
UPDATE table1 t1
SET t1.fieldA = (SELECT T2.fieldB,SDO_NN_DISTANCE(1) distance
FROM table1 T1, table2 T2
WHERE
(sdo_nn(t1.geometry,t2.geometry,'SDO_NUM_RES=1',1)= 'TRUE')
ORDER BY DIST
)
WHERE EXISTS(
SELECT 1
FROM table2 t2
WHERE sdo_nn(t1.geometry, t2.geometry,'SDO_NUM_RES=1',1)='TRUE'
AND(t2.cell_name = 'string1' or t2.cell_name = string2')AND t1.fieldA = NULL
);
In the select sentence of the subquery i get an error because i only use one field(t1.fieldA), but in the sentence i use the operator SDO_NN_DISTANCE(1) and the sql developer count this operator like another field. What is the correct way to write this sentence? I only use sql because i need to insert this code in vba
Thanks!!!
Obviously, you can't (simplified)
set t1.fieldA = (t2.fieldB, distance) --> you want to put two values into a single column
Therefore, get fieldB alone from the subquery which uses analytic function (row_number) to "sort" rows by sdo_nn_distance(1) desc; then get the first row's fieldB value.
Something like this (I hope I set the parenthesis right):
UPDATE table1 t1
SET t1.fieldA =
(SELECT x.fieldB --> only fieldB
FROM (SELECT T2.fieldB, --> from your subquery
SDO_NN_DISTANCE (1) distance,
ROW_NUMBER ()
OVER (ORDER BY sdo_nn_distance (1) DESC) rn
FROM table1 T1, table2 T2
WHERE (sdo_nn (t1.geometry,
t2.geometry,
'SDO_NUM_RES=1',
1) = 'TRUE')) x
WHERE rn = 1) --> where RN = 1
WHERE EXISTS
(SELECT 1
FROM table2 t2
WHERE sdo_nn (t1.geometry,
t2.geometry,
'SDO_NUM_RES=1',
1) = 'TRUE'
AND ( t2.cell_name = 'string1'
OR t2.cell_name = 'string2')
AND t1.fieldA IS NULL);

Oracle - Invalid relational operator when I'm using EXISTS

I have the following query that was given to me, where the returned record is removed from the table et_fact_reclam_ter_his_misc when the condition is met:
DELETE FROM et_fact_reclam_ter_his_misc
WHERE num_siniest || num_exped IN
(SELECT DISTINCT num_siniest || num_exped
FROM et_fact_reclam_ter_his_misc t1
WHERE NOT EXISTS (SELECT *
FROM et_fact_reclam_ter_misc t2
WHERE t1.num_siniest = t2.num_siniest));
I've been searching, and found that using EXISTS instead of IN will improve query performance. But I have run into 2 errors. The first is an error message that appears when I replace the IN operator with EXISTS:
DELETE FROM et_fact_reclam_ter_his_misc
WHERE num_siniest || num_exped EXISTS
(SELECT DISTINCT num_siniest || num_exped
FROM et_fact_reclam_ter_his_misc t1
WHERE NOT EXISTS (SELECT *
FROM et_fact_reclam_ter_misc t2
WHERE t1.num_siniest = t2.num_siniest));
ORA-00920: invalid relational operator
The second is when I try to nest a SELECT inside the DELETE, but the number of rows returned are different:
DELETE FROM et_fact_reclam_ter_his_misc
WHERE EXISTS
(SELECT FROM et_fact_reclam_ter_his_misc
WHERE num_siniest || num_exped IN
(SELECT DISTINCT num_siniest || num_exped
FROM et_fact_reclam_ter_his_misc t1
WHERE NOT EXISTS
(SELECT *
FROM et_fact_reclam_ter_misc t2
WHERE t1.num_siniest = t2.num_siniest)));
I appreciate any help to improve query performance
Could you try below, not the best approach to concatenate fields for joins,
DELETE FROM et_fact_reclam_ter_his_misc A
WHERE EXISTS
( SELECT 1 FROM
(SELECT DISTINCT num_siniest || num_exped
FROM et_fact_reclam_ter_his_misc t1) B
WHERE A.num_siniest|| A.num_exped = B.num_siniest || B.num_exped
AND NOT EXISTS (SELECT 1
FROM et_fact_reclam_ter_misc t2
WHERE B.num_siniest = t2.num_siniest));
Seems like the concatenated columns are numbers and it would force oracle to cast it to char which could hinder performance.Below one should be faster if you are dealing with lots of records.
DELETE FROM et_fact_reclam_ter_his_misc A
WHERE EXISTS
( SELECT 1 FROM
(SELECT DISTINCT num_siniest, num_exped
FROM et_fact_reclam_ter_his_misc t1) B
WHERE A.num_siniest = B.num_siniest
AND A.num_exped = B.num_exped
AND NOT EXISTS (SELECT 1
FROM et_fact_reclam_ter_misc t2
WHERE B.num_siniest = t2.num_siniest));
DISTINCT will overkill, substituting with group by will definitely be far better, so the best one will be :
DELETE FROM et_fact_reclam_ter_his_misc A
WHERE EXISTS
( SELECT 1 FROM
(SELECT num_siniest, num_exped,count(1)
FROM et_fact_reclam_ter_his_misc t1
group by num_siniest, num_exped) B
WHERE A.num_siniest = B.num_siniest
AND A.num_exped = B.num_exped
AND NOT EXISTS (SELECT 1
FROM et_fact_reclam_ter_misc t2
WHERE B.num_siniest = t2.num_siniest));
Looks like this might do it:
delete et_fact_reclam_ter_his_misc t1
where not exists
( select * from et_fact_reclam_ter_misc t2
where t2.num_siniest = t1.num_siniest
);
In the original version, the first level subquery seems to be querying the same table that is being deleted, just in order to construct a not exists subquery. I suspect that all you want to do is delete his rows where num_siniest does not exist in the main table. Some sample data and expected results would make this clearer.

Query fails to execute after converting a column from Varchar2 to CLOB

I have a oracle query
select id from (
select ID, ROW_NUMBER() over (partition by LATEST_RECEIPT order by ID) rownumber
from Table
where LATEST_RECEIPT in
(
select LATEST_RECEIPT from Table
group by LATEST_RECEIPT
having COUNT(1) > 1
)
) t
where rownumber <> 1;
The data type of LATEST_RECEIPT was earlier varchar2(4000) and this query worked fine. Since the length of the column needs to be extended i modified it to CLOB, after which this fails. Could anyone help me fix this issue or provide a work around?
You can change your inner query to look for other rows with the same last_receipt value but a different ID (assuming ID is unique); if another row exists then that is equivalent to your count returning greater than one. But you can't simply test two CLOB values for equality, you need to use dbms_lob.compare:
select ID
from your_table t1
where exists (
select null from your_table t2
where dbms_lob.compare(t2.LATEST_RECEIPT, t1.LATEST_RECEIPT) = 0
and t2.ID != t1.ID
-- or if ID isn't unique: and t2.ROWID != t1.ROWID
);
Applying the row number filter is tricker, as you also can't use a CLOB in the analytic partition by clause. As André Schild suggested, you can use a hash; here passing the integer value 3, which is the equivalent of dbms_crypto.hash_sh1 (though in theory that could change in a future release!):
select id from (
select ID, ROW_NUMBER() over (partition by dbms_crypto.hash(LATEST_RECEIPT, 3)
order by ID) rownumber
from your_table t1
where exists (
select null from your_table t2
where dbms_lob.compare(t2.LATEST_RECEIPT, t1.LATEST_RECEIPT) = 0
and t2.ID != t1.ID
-- or if ID isn't unique: and t2.ROWID != t1.ROWID
)
)
where rownumber > 1;
It is of course possible to get a hash collision, and if that happened - you had two latest_receipt values which both appeared more than once and both hashed to the same value - then you could get too many rows back. That seems pretty unlikely, but it's something to consider.
So rather than ordering you can only look for rows which have the same lastest_receipt and a lower ID:
select ID
from your_table t1
where exists (
select null from your_table t2
where dbms_lob.compare(t2.LATEST_RECEIPT, t1.LATEST_RECEIPT) = 0
and t2.ID < t1.ID
);
Again that assumes ID is unique. If it isn't then you could still use rowid instead, but you would have less control over which rows were found - the lowest rowid isn't necessarily the lowest ID. Presumably you're using this to dine rows to delete. If you actually don't mind which row you keep and which you delete then you could still do:
and t2.ROWID < t1.ROWID
But since you are currently ordering that probably isn't acceptable, and hashing might be preferable, despite the small risk.

How to delete multiple rows with 2 columns as composite primary key in SQLite?

I need to delete some rows in a SQLite table with two columns as primary key, like this:
DELETE FROM apt_lang
WHERE (apt_fk, apt_lang_fk) NOT IN ((42122,"en"),(42123,"es"),(42123,"en"))
This works on Oracle and MySQL but not in SQLite.
Can anybody help me?
First, find out which rows you want to delete.
The easiest way is with a join:
SELECT *
FROM apt_lang
JOIN (SELECT 42122 AS apt_fk, 'en' AS apt_lang_fk UNION ALL
SELECT 42123 , 'es' UNION ALL
SELECT 42123 , 'en' )
USING (apt_fk, apt_lang_fk)
To use this with a DELTE, either check with EXISTS for a match:
DELETE FROM apt_lang
WHERE NOT EXISTS (SELECT 1
FROM apt_lang AS a2
JOIN (SELECT 42122 AS apt_fk, 'en' AS apt_lang_fk UNION ALL
SELECT 42123 , 'es' UNION ALL
SELECT 42123 , 'en' )
USING (apt_fk, apt_lang_fk)
WHERE apt_fk = apt_lang.apt_fk
AND apt_lang_fk = apt_lang.apt_lang_fk)
or get the ROWIDs of the subquery and check against those:
DELETE FROM apt_lang
WHERE rowid NOT IN (SELECT apt_lang.rowid
FROM apt_lang
JOIN (SELECT 42122 AS apt_fk, 'en' AS apt_lang_fk UNION ALL
SELECT 42123 , 'es' UNION ALL
SELECT 42123 , 'en' )
USING (apt_fk, apt_lang_fk))
This should work:
DELETE FROM apt_lang WHERE (apt_fk, apt_lang_fk) NOT IN (VALUES (42122,"en"),(42123,"es"),(42123,"en"))
Yes, it's possible to delete rows from SQLite based on a subquery that builds on multiple columns. This can be done with SQLite's concatenate "||" operator. It might help to show an example.
Setup:
create table a (x,y);
insert into a values ('A','B');
insert into a values ('A','C');
create table b (x,y);
insert into b values ('A','C');
insert into b values ('A','X');
Show Tables:
select * from a;
A|B
A|C
select * from b;
A|C
A|X
Assuming you want to delete from table a rows where column x and column y don't match with table b, the following select will accomplish that.
delete from a where x||y not in (select a.x||a.y from a,b where a.x=b.x and a.y=b.y);
Result:
select * from a;
A|B
Summary
This relies on concatenating several columns into one with the "||" operator. Note, it will work on calculated values too, but it might require casting the values. So, just a few conversions to note with the "||" operator...
select 9+12|| 'test';
21 -- Note we lost 'test'
select cast(9+12 as text)|| 'test';
21test -- Good! 'test' is there.

record types that weren't found for a specific value in oracle query

I have this query
Select distinct p_id, p_date,p_city
from p_master
where p_a_id in(1,2,5,8,2,1,10,02)
and my IN clause contains 200 values. How do I get to know which ones weren't returned by the query. Each value in the IN clause may have a record in some cases they don't. I want to know all the records that weren't found for any selected p_a_id type.
Please help
This will do the trick but I'm sure there's an easier way to find this out :-)
with test1 as
(select '1,2,5,8,2,1,10,02' str from dual)
select * from (
select trim(x.column_value.extract('e/text()')) cols
from test1 t, table (xmlsequence(xmltype('<e><e>' || replace(t.str,',','</e><e>')|| '</e></e>').extract('e/e'))) x) cols
left outer join
(Select count(*), p_a_id from p_master where p_a_id in (1,2,5,8,2,1,10,02) group by p_a_id) p
on p.p_a_id = cols.cols
where p_a_id is null
;

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